Device for operating a short arc discharge mercury lamp

Abstract

A short arc ultra-high pressure mercury lamp, at least one of the electrodes of which has a melted part towards the electrode head and a coil part which extends from the melted part continuously and integrally with it in a direction away from the electrode head, avoids blackening of the tube wall and achieves a long service life by the provision of a power supply which supplies the discharge lamp with direct current when operation is starting and afterwards supplies it with an alternating current, the direct current supplied by the power supply to the discharge lamp being initially 0.3 to 0.6 times as great as the rated current and afterwards increasing to 1.0 to 2.0 times are great as the rated current.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to a device for operating a short arc discharge lamp. The invention relates especially to a device for operating an ultra-high pressure mercury lamp in which an arc tube is filled with at least 0.15 mg / mm3 of mercury and in which the mercury vapor pressure during operation is at least 110 atm, and which is used for a light source for a projector device, such as a liquid crystal display device or a DLP (digital light processor using a DMD (digital micro mirror device) or the like.[0003]2. Description of the Related Art[0004]In a projection-type display device, there is a demand for illumination of images onto a rectangular screen in a uniform manner and with adequate color rendering. Therefore, the light source is a metal halide lamp which is filled with mercury and a metal halide. Furthermore, recently smaller and smaller metal halide lamps, and more and more often point light sources are being pro...

AI Technical Summary

Benefits of technology

[0009]A primary object of the present invention is to devise a short arc ultra-high pressure mercury lamp in which the above described blackening of the tube wall as a result of the tungsten of the electrodes being transported to the inner surface of the discharge vessel is suppressed and which has a long service life.

[0017]It was found that, as a result of this phenomenon, by the contact of the discharge arc which proceeds from the back end of the coil with the inside surface of the discharge vessel, vaporization of the silica glass comprising the discharge vessel has a great effect on the transport of the tungsten.

[0018]It was confirmed that this phenomenon clearly occurs especially in a discharge lamp with electrodes which have a melt part and a coil part on the back end and with a small, extremely short distance between the electrodes and the inside surface of the discharge vessel.

[0019]The inventors have found that, to achieve the above described new object with respect to a short arc discharge lamp, it is effective to regulate the current supply from the power supply to the discharge lamp at the beginning of lamp start-up.

Problems solved by technology

This blackening of the tube wall causes a reduction of the light intensity and furthermore breaking of the discharge vessel by increasing the thermal load on the tube wall in the case to considerable blackening of the tube wall; this leads to a shortening of the service life of the lamp.

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